What can I do to remove these bolts???

I've got two 7/16 bolts holding what looks like an aluminum plate on the back of my 383. These bolts are recessed in the plate and the plate keeps me from putting the torque to the rear main bearing so I can pull the crank. They look to be rounded and I can't get a socket on them. Recession is only wide enough to get the socket in, and no more. Anyone run into this before? Previous owner may have rounded them, but this is my first 383 tear down and this has got me stopped dead in my tracks.